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  Java Practices -> Reading and writing Serializable objects
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<div class='page-title'>Reading and writing Serializable objects</div>

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<br>Reading and writing&nbsp;<tt><a href="http://java.sun.com/javase/6/docs/api/java/io/Serializable.html">Serializable</tt></a>
objects is very similar to reading and writing text :
<ul>
<li>
it is almost always a good idea to use buffering (default size is 8K)</li>

<li>
it is often possible to use abstract base class references, instead of
references to concrete classes</li>

<li>
there is always a need to pay attention to exceptions; in particular, <tt><a href="http://java.sun.com/javase/6/docs/api/java/io/IOException.html">IOException</a></tt>
and <tt><a href='http://download.oracle.com/javase/6/docs/api/java/lang/ClassNotFoundException.html'>ClassNotFoundException</a></tt></li>
</ul>
The <tt>close</tt> method :
<ul>
<li>
always needs to be called, or else resources will leak</li>

<li>
will automatically flush the stream, if necessary</li>

<li>
calling <tt>close</tt> on a "wrapper" stream will automatically call <tt>close</tt>
on its underlying stream</li>

<li>
closing a stream a second time has no consequence</li>
</ul>
<b>Example</b>
<p>Here, a <tt>List</tt> of <tt>String</tt> objects is serialized and then
deserialized.
<br>
<PRE>

<span class='keyword'>import</span> java.io.*;
<span class='keyword'>import</span> java.util.*;
<span class='keyword'>import</span> java.util.logging.*;

<span class='keyword'>public</span> <span class='keyword'>class</span> ExerciseSerializable {

  <span class='keyword'>public</span> <span class='keyword'>static</span> <span class='keyword'>void</span> main(String... aArguments) {
    <span class='comment'>//create a Serializable List
</span>    List&lt;String&gt; quarks = Arrays.asList(
      <span class='literal'>"up"</span>, <span class='literal'>"down"</span>, <span class='literal'>"strange"</span>, <span class='literal'>"charm"</span>, <span class='literal'>"top"</span>, <span class='literal'>"bottom"</span>
    );

    <span class='comment'>//serialize the List
</span>    <span class='comment'>//note the use of abstract base class references
</span>
    <span class='keyword'>try</span>{
      <span class='comment'>//use buffering
</span>      OutputStream file = <span class='keyword'>new</span> FileOutputStream( <span class='literal'>"quarks.ser"</span> );
      OutputStream buffer = <span class='keyword'>new</span> BufferedOutputStream( file );
      ObjectOutput output = <span class='keyword'>new</span> ObjectOutputStream( buffer );
      <span class='keyword'>try</span>{
        output.writeObject(quarks);
      }
      <span class='keyword'>finally</span>{
        output.close();
      }
    }  
    <span class='keyword'>catch</span>(IOException ex){
      fLogger.log(Level.SEVERE, <span class='literal'>"Cannot perform output."</span>, ex);
    }

    <span class='comment'>//deserialize the quarks.ser file
</span>    <span class='comment'>//note the use of abstract base class references
</span>    
    <span class='keyword'>try</span>{
      <span class='comment'>//use buffering
</span>      InputStream file = <span class='keyword'>new</span> FileInputStream( <span class='literal'>"quarks.ser"</span> );
      InputStream buffer = <span class='keyword'>new</span> BufferedInputStream( file );
      ObjectInput input = <span class='keyword'>new</span> ObjectInputStream ( buffer );
      <span class='keyword'>try</span>{
        <span class='comment'>//deserialize the List
</span>        List&lt;String&gt; recoveredQuarks = (List&lt;String&gt;)input.readObject();
        <span class='comment'>//display its data
</span>        <span class='keyword'>for</span>(String quark: recoveredQuarks){
          System.out.println(<span class='literal'>"Recovered Quark: "</span> + quark);
        }
      }
      <span class='keyword'>finally</span>{
        input.close();
      }
    }
    <span class='keyword'>catch</span>(ClassNotFoundException ex){
      fLogger.log(Level.SEVERE, <span class='literal'>"Cannot perform input. Class not found."</span>, ex);
    }
    <span class='keyword'>catch</span>(IOException ex){
      fLogger.log(Level.SEVERE, <span class='literal'>"Cannot perform input."</span>, ex);
    }
  }

  <span class='comment'>// PRIVATE //
</span>
  <span class='comment'>//Use Java's logging facilities to record exceptions.
</span>  <span class='comment'>//The behavior of the logger can be configured through a
</span>  <span class='comment'>//text file, or programmatically through the logging API.
</span>  <span class='keyword'>private</span> <span class='keyword'>static</span> <span class='keyword'>final</span> Logger fLogger =
    Logger.getLogger(ExerciseSerializable.<span class='keyword'>class</span>.getPackage().getName())
  ;
} 
</PRE>
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<div class='topic-section'>See Also :</div>
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  <a href='TopicActiona0d7-2.html?Id=8'>Always close streams</a> <br>
 
  
  <a href='TopicActione028-2.html?Id=25'>Finally and catch</a> <br>
 
  
  <a href='TopicAction693b-2.html?Id=43'>Recovering resources</a> <br>
 
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